Apparatus for preventing unthreading of members in a well bore



Oct; 1969 J. c. GRAFF 3,475,040

APPARATUS FOR PREVENTING UNTHREADING OF MEMBERS IN A WELL BORE Filed Sept. 29, 1967 I I I I I I I I I I I r H Jew/ C. Gra ff United States Patent 3,475,040 APPARATUS FOR PREVENTING UNTHREADING OF MEMBERS lN A WELL BORE Jerry C. Gralf, Houston, Tex., assignor to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed Sept. 29, 1967, Ser. No. 671,740 Int. Cl. F161 55/00; F16b 39/00 US. Cl. 285-89 4 Claims ABSTRACT OF THE DISCLOSURE The particular embodiment disclosed herein as illustrative of one form of the invention is a coupling mechanism to prevent inadvertent unthreading of members in a well bore, and includes a skirt on one member laterally spaced from the other member to provide an annulus, segmented means in the annulus coupled against longitudinal movement to the other member, and stop means connected to the skirt and arranged to retain the segmented means coupled to the other member and to abut the segmented means in case unthreading force is applied to the members to prevent unthreading of said members from one another.

This invention relates to well tool couplings, and more specifically to well tool couplings which cannot be inadvertently unthreaded while located in a well bore by the application of torque to the coupling which is reverse in direction to the make-up torque for the coupling.

Many well tools have threadedly coupled parts which are rotated in a well bore. The make-up direction for the threaded coupling is normally in the same direction as the rotation so that the coupling is not loosened and unscrewed during operation of the tool in the Well. However, it is sometimes necessary to apply reverse torque to a tool in an attempt to purposely loosen the threaded coupling. This may occur, for example, where a downhole tool has been stuck in the well bore and a safety joint must be operated to disconnect from the stuck tool. Or, as those who are skilled in this art will appreciate, reversed torque may be applied to the drill pipe and a string shot or the like lowered and fired adjacent to the particular threaded connection in order to facilitate unscrewing the connection.

Of course, it would be undesirable to inadvertently unscrew other threaded couplings than the one intended and thus leave even more stranded objects in the well to be fished out. This is particularly true with such tools as bumper subs and jars, which are relatively expensive items of equipment, so that an operator would take precaution-s not to inadvertently dismember the equipment and leave parts thereof in the well.

The present invention provides an apparatus for preventing unthreading of connections in a well bore by the application of the reverse torque through the connections. Incorporation of the present invention in the well equipment such as bumper subs and jars will prevent the inadvertent dismemberment of the tool when situations arise where reverse torque must be applied through the tool to other equipment in the well.

In accordance with concepts of the present invention, one portion of a threaded connection, such as the female portion, has a section which is recessed away from the other portion, such as the male portion. Coengageable stop means are positioned between the portions and arranged for engagement with each other should the portions try to unscrew from one another. The stop means includes a holding ring on the female portion having a shoulder which extends inwardly toward the male portion to provide a stop surface which faces in the back-off direction. The stop means further includes a separable member which is held in coupled relation to the male portion by the holding ring and which has a stop surface facing the holding ring stop surface. Accordingly, should the threaded portions try to unscrew from one another, the stop surfaces will engage to prevent further longitudinal relative movement, thereby preventing unthreading of one portion from the other. When it is desired to purposely unscrew the portions, the holding ring may be conveniently removed.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by way of illustration and example of a preferred embodiment taken in conjunction with the accompanying drawings, in which:

FIGURE 1 illustrates schematically a bumper sub for use in a string of well tools and which incorporates the principles of the invention;

FIGURE 2 is an enlarged sectional view of the coupling parts of the present invention to more clearly illustrate the structural details thereof; and

FIGURE 3 is a cross-section on line 3--3 of FIG- URE 2.

A bumper sub 10 which incorporates the present invention is shown schematically in FIGURE 1 to include an upper sub 11 having threads 12 for connecting the drill pipe 13 or the like. The sub 11 is coupled to an elongate mandrel 14 by threads 15, and an O-ring seal 16 can prevent fluid leakage through the threads. These threads 15, in conventional manner for down-hole usage, are right hand threads so as to be compatible with the make-up direction of the numerous joints in the drill pipe. A tubular housing 18 is mounted around the mandrel 14 and has lower threads 15 for connecting to drill pipe or to another well tool. The housing 18 can be conveniently formed by a spline sub 19 which is threadedly connected to a lower sub 20 in a fluid-tight manner. In order to transmit rotation of the drill pipe 13 through the mandrel 14 to the housing 18, coengageable splines 22 and 23 are provided on the exterior of the mandrel and in the interior of the housing to co-rotatively and slidably couple the mandrel and housing to each other. The mandrel 14 and the upper sub 11 have respective open hole bores 24 and 25 for fluid circulation through the tool.

The housing 18' has an inwardly extending shoulder section 27 which provides an anvil against which the mandrel spline 22, providing a hammer, can impact upon upward movement of the mandrel 14 relative to the housing. Thus, jarring force can be applied to a stuck well tool or other object which is coupled to the lower end of the housing 18 by raising the mandrel 14 until the splines 22 strike the shoulder section 27. Moreover, the upper sub 11 can be impacted against the upper end of the housing 18 by lowering the mandrel 14 to impart downward jarring force to the stuck object, the lower end portions of the upper sub providing the hammer, and the upper end surface of the housing providing the anvil.

The spline section 19 of the housing 18 can be sealed from well fluids for enhanced operational capabilities of the tool. Thus, appropriate seals 30 seal between the shoulder section 27 and the mandrel 14, and a sliding balance piston 31 is positioned between the lower end portion of the spline section 19 and the mandrel, the balance piston having appropriate seals 32 and 33 to prevent fluid leakage. The closed spline chamber 34 thus formed can contain a suitable lubricating fluid to ensure easy working of parts. Inasmuch as the upper portion of the mandrel 14 is exposed to well fluids when the mandrel is telescoped upwardly, a wiper ring or the like can be arranged to wipe the exposed surfaces clean as they pass into the chamber 34.

It will be appreciated that it is desirable to prevent the threads 15 which couple the upper sub 11 to the mandrel 14 from backing off in the well bore, since this occurrence would dismember the bumper sub 10. In accordance, with the principles of the present invention, the aforementioned happenstance cannot occur in the well bore, as will be more apparent in connection with FIGURE 2. As shown, the lower portion of the top sub 11 is provided with a skirt 40, which extends along the mandrel 14 and which is laterally spaced therefrom to define an annulus. The skirt can be internally threaded at 41, and the adjacent section of the mandrel 14 can also be threaded at 42. A holding ring 43 is coupled to the skirt 40 by threads 44, for example, and has an internal recess 45 which provides an upwardly facing shoulder 46. A stop means 48 is located within the recess 45 and has threads 49 which engage the companion threads of the mandrel. The stop means 48 can take the form of a collar which is diametrically cut through so as to be constituted by two C-shaped segments 50 and 51 as shown in FIGURE 3. The segments are sized to fit snugly within the recess 45 with their outer peripheries engaging the side wall of the recess 45 to prevent outward movement. Thus, the holding ring 43 retains the segment threads 49 in engagement with the mandrel threads 42, and the stop element 48 cannot move longitudinally with respect to the mandrel 14. Should reverse torque be applied to the threads 15 suflicient to overcome the make-up load, the upper sub 11 cannot be backed off of the mandrel 14 to any significant extent because the shoulder 46 on the holding ring 43 will abut or engage the stop means 48 to prevent further advancement of the top sub 11 relative to the mandrel 14 in the backing-off direction.

To assemble the present invention, the mandrel 14 is extended relative to the housing 18 and the holding ring 43 positioned on the mandrel below the threads 42. Then the top sub 11 is threaded onto the mandrel 14 and the segments 50 and 51 are placed under the skirt 40 and in engagement with the threads 42. Finally, the holding ring 43 is threadedly connected to the skirt 40 so that that ring retains the segments 50 and 51 inwardly in coupled relationship to the mandrel 14. It is preferable to locate the stop means 48 on the mandrel 14 such that the upper ends of the segments 50 and 51 are spaced a small distance away from sub shoulder 53, and the lower ends are also spaced a small distance away from the shoulder 46. Accordingly, the threaded joint 15 can be tightened as much as desired on the rig floor prior to lowering into the well and the stop means 48 will not impede such tightening. Moreover, the threads 15 can be loosened to some extent on the rig floor with available equipment when the tool is withdrawn from the well, thereby facilitating later dis assembly of the tool for maintenance, repair, or the like. Of course, the coupling mechanism of the present invention can be readily disassembled by simply unthreading the holding ring 43 from the skirt 40.

It will be appreciated from the close inspection of the present invention that the holding ring 43 is a relatively small part in comparison to the mandrel 14, for example. Accordingly, the holding ring 43 has a small mass and rotational inertia and is not subject to significant backoff force due to sudden and repeated stoppage of rotation of the bumper sub 10 during a typical operation.

It will be apparent that a new and improved apparatus has been disclosed for preventing unthreading of joints in a well bore when reverse torque is applied thereto. Changes or modifications may be made in the disclosed embodiment by those skilled in the art without departing from the concepts involved.

What is claimed is:

1. Apparatus for preventing unthreading of threadably coupled tubular members in a well bore comprising: a skirt on one threaded member extending along the other threaded member and spaced therefrom to provide an annulus, separate arcuate means in said annulus; means to couple said arcuate means to said other member to prevent longitudinal movement relative thereto; and holding means bet-ween said members threaded to said skirt and being radially spaced from the outer peripheral surface of said other member, said holding means having a stepped internal surface providing a first axially extending locking surface engageable with a peripheral surface of said arcuate means for retaining said arcuate means coupled to said other member and a second transversely extended locking surface engageable with an end surface of said arcuate means to prevent longitudinal relative movement between said members.

2. Apparatus for preventing unthreading of a threaded connection between inner and outer tubular members in a well bore, comprising: a skirt on said outer member extending along a portion of said inner member; holding means releasably coupled to said skirt, said holding means having a stepped internal surface radially spaced from the outer periphery of said inner member that provides together with said skirt and said inner member an axially extending annular cavity; a stop ring assembly including a plurality of separate arcuate segments positioned within said cavity and contracted around said portion of said inner member; and means for coupling said stop ring assembly against longitudinal movement relative to said inner member, said holding means and said stop ring assembly having axially extending wall surfaces that are coengageable to retain said stop ring assembly contracted around said inner member, said holding means and said stop ring assembly having transversely extending wall surfaces that are coengageable to prevent unthreading of said threaded connection between said inner and outer members.

3. The apparatus of claim 2 wherein said stop ring assembly is positioned within said cavity with said transversely extending wall surfaces in spaced apart relationship to each other to enable loosening of said threaded connection prior to releasing the coupling between said holding means and said skirt.

4. The apparatus of claim 2 wherein said stop ring assembly is positioned within said cavity intermediate the ends thereof to enable tightening of said threaded connection after said holding means has been coupled to said skirt as well as loosening of said threaded connection prior to releasing the coupling between said holding means and said skirt.

References Cited UNITED STATES PATENTS 1,293,180 2/1919 Pace 15119 2,206,873 7/1940 Boynton 285-89 2,226,547 12/ 1940 Boynton 285-89 3,321,217 5/1967 Ahlstone 285-86 3,395,934 8/1968 Rosan et al 285-92 FOREIGN PATENTS 295,371 4/1932 Italy. 352,880 9/1937 Italy.

THOMAS F. CALLAGHAN, Primary Examiner US. Cl. X. R. 15l2, 28 

